Question

The standard potentials (\( E^\circ \)) for the Fe\(^{3+}\)/Fe and Fe\(^{3+}\)/Fe\(^{2+}\) couples are -0.04 V and +0.76 V, respectively.
Given: Faraday constant = 96500 C mol\(^{-1}\)
The value for \( E^\circ \) (Fe\(^{2+}\)/Fe) in V is ............... (rounded off to two decimal places)

Hint:

The standard electrode potential for a redox couple can be calculated by using the known potentials for related half-reactions.

Answer 1

We are given the standard electrode potentials for two half-reactions: \[ E^\circ ({Fe}^{3+}/{Fe}) = -0.04 \, {V}, \quad E^\circ ({Fe}^{3+}/{Fe}^{2+}) = +0.76 \, {V} \] To calculate \( E^\circ ({Fe}^{2+}/{Fe}) \), we can use the Nernst equation, which relates the standard electrode potential for the two half-reactions: \[ E^\circ ({Fe}^{2+}/{Fe}) = E^\circ ({Fe}^{3+}/{Fe}) + E^\circ ({Fe}^{3+}/{Fe}^{2+}) \] Substituting the values: \[ E^\circ ({Fe}^{2+}/{Fe}) = -0.04 + 0.76 = -0.46 \, {V} \] Thus, the value of \( E^\circ ({Fe}^{2+}/{Fe}) \) is -0.46 V.